The project is focused on the elucidation of molecular mechanisms that operate during immune activation. A better understanding of such mechanisms will provide the foundation for identifying molecular defects which underlie various immunologic diseases, and it will also provide potential new targets for therapeutic interventions aimed at controlling destructive inflammatory reactions. Specifically, we wish to delineate signal-transducing events within immunologically relevant cells in response to pathogens, stress and/or mitogens. One of the most central responses to immunologic challenges is the production of cytokines belonging to the tumor necrosis factor (TNF) family, which in turn control many aspects of the final immune response by signaling through TNF receptors present on many cells. A primary target of TNF within cells is the transcription factor NF-kappaB, which in turn induces expression of many genes with functions critical to controlling pathogens; it is also essential for expression of HIV and thus productive infection by this virus. We have begun to identify proteins which represent novel intracellular links in the relay of the signals which emanate from the cell surface after stimulation by TNF cytokines. Similarly, we have identified components involved in targeting NF-(B after stimulation through the T-cell receptor (TCR). Ultimately we intend to define the entire chain of events by which the TNF cytokines and the antigen stimulation of the TCR and other ligands may activate NF-kappaB. As part of these analyses, we are also asking how the HTLV I retroviral Tax protein, which contributes to transformation of human T cells, can interphase with known signaling cascades to activate NF-kappaB; in addition, we are investigating various intracellular kinases for their ability to activate NF-kappaB and whether or not they may lie on pathways activated by TNF cytokines or the TCR. We have cloned a kinase (MEKK3) which functions within MAPKinase pathways and which is capable of targeting NF-kappaB. The kinase was cloned as part of an effort to identify novel genes involved in immune responses. We have developed a system which allows us to study the biologic effects of turning on only this kinase and we have discovered a dramatic effect on control of the cell cycle, which represents a novel finding.